Added support of configuration play2 system properties
Fixed dubug execution
Update src/site/markdown/usage.md.vm

Added documentation for play2 system properties configuration usage
Added me as contributor 
Explicit imports. Renamed method from getPlay2Arguments() to getPlay2SystemPropertiesArguments()
Merge pull request #30 from xaoc3dgraph/master

I consider it merge-ready. 

Added support of  system properties configuration for play2 execution test/run/debug command